Whats the total area of a covered box with a length of 4 ft, a width of 3 ft, and a height of 6 ft

Volume is "L x W x H". (Length x Width x Height)

The top and bottom will be 4 x 3 = 12 sq ft.

2 sides each 4 x 6 = 24 x 2 = 48 sq ft.

2 sides each 3 x 6 = 18 x 2 = 36 sq ft.

Area = 24 + 36 + 48 sq ft = 108 sq ft.

The formula for the area of a 3D rectangle is A=B*H*W (Area=Base*Hight*Width) Length and base are the same thing, so 4*3*6 = 72. You would then make it 72²ft, for cubic measurement.